This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Increased hair cortisol concentrations have been correlated with stress exposure in both human and non-human primates, and hair cortisol is now gaining attention as a biomarker for stress-related health problems. However, to date, no studies have examined its usefulness for predicting future mental health problems. This study determined whether hair cortisol was a significant predictor of later anxiety in young rhesus macaques (Macaca mulatta).